SAN FRANCISCO – The master captain of the freighter that hit a bridge and spilled oil into San Francisco Bay told investigators that the fog was so thick he could not see the ship's bow and that the pilot ordered a sharp turn before the crash, according to court documents.

Last month, federal prosecutors charged the freighter's pilot, Capt. John Cota, with environmental crimes stemming from the Nov. 7 accident, when the Cosco Busan sideswiped a support tower of the San Francisco-Oakland Bay Bridge.

The crash fouled the bay with 53,000 gallons of sludgelike fuel, killing or injuring thousands of birds and temporarily closing several beaches.

Yesterday, a judge unsealed documents that prosecutors filed to prevent six Chinese crew members dubbed “material witnesses” from leaving San Francisco, including master Capt. Mao Cai Sun. Cota's job was to pilot the ship out of the bay, when Sun would take over. Sun told investigators the fog was so thick that “in other countries, the port would have been closed,” according to the documents. He also said Cota stopped using the ship's radar system and relied on an electronic chart viewer to navigate under the Bay Bridge. “The ship's radar is the primary tool of navigation,” the documents state.

Crew members said the ship was traveling too fast, and prosecutors allege that Cota forgot a tugboat was tied to the freighter.

“As a result of the sudden and sharp turn, the ship created five to six foot waves in its wake,” the documents state. “The tugboat Revolution had to release all of its lines as an emergency measure to avoid being capsized by the speed and height of the waves.”

Cota will refuse to testify next week at a government hearing investigating the crash, his lawyer, Jeff Bornstein, said yesterday.

Bornstein blamed the Coast Guard and others for the accident, saying the Guard had the responsibility to track the ship and warn the pilot that a crash was imminent. Cota has said the ship's radar wasn't reliable and that there was confusion about symbols on at least one of the navigational charts.